Vinyl records use grooves on the disc to encode the music. But not the
Evil Eye optical synth by Belgian collective Indianen:

Instead of cutting grooves onto a surface, custom software allows
the artists to design and print black-and-white waveform patterns as
PDFs, which are then screenprinted onto 12-inch optical discs and played
back on a turntable using specialized light-sensing hardware instead
of a needle. The waveforms can be either shaped manually in the software
or imported / modified from existing patterns.

The "eye" hardware's designer, Tim Knapen, says he opted
not to use a smartphone camera as the sensor, because it would have
unnecessarily complicated the process. "We use a simple light-to-voltage
converter that doesn't do any processing. An iPhone app would require
some visual processing but more importantly also some kind of synthesizer.
In the setup we used, all the sound is encoded in the disks and there
is no need for anything digital."